Mr. McPherson seems absorbed in his fantasy.
“Runaway climate change” is the major phantom terrorizing this vastly overcredentialed Guy McPherson, and it is not possible. Even if carbon dioxide rose to ten times its current planet-wide levels, neither the atmospheric temperatures nor the mortality of animal life would be noticeably affected.
Plant growth, on the other hand, would be greatly accentuated, and the profusion that followed would blanket the well-watered portions of the planet everywhere. Even in the depths of the ocean and major sources and tributaries of water, the plant growth would proliferate to an astounding degree, perhaps even RAISING the oxygen content of a atmosphere by some small amount.
You understand, of course, that oxygen is the second most corrosive element in the Universe, and large quantities of elemental oxygen may itself present a serious hazard. Think of how brightly things shall blaze if they catch fire, or how quickly metallic elements would turn to corrosion and crumble in a high-oxygen environment.
Or maybe, life has already evolved and is adapted perfectly to those conditions.
I’ll bet the professor is a registered Democrat.